The Secret To a Chameleon’s Color Change—It’s Crystals

Ever wonder exactly how chameleons are able to change their spots and camouflage themselves under the bright forest canopy? Well you're not likely to guess the intriguing method involved. It turns out that while the chameleons are docile and soft, for the most part, this interesting species has a lot more in common with diamonds than anyone ever thought.

Beneath the epidermal layer of skin that protects chameleons, the lizard species has different layers of cells below that help give them their unique pigmentation. But amongst these layers also lie tiny crystals that allow their color-changing ability to take shape. Known as "iridophores", the subsurface crystals are key to a chameleon's color.

In a new study published this week in the journal Nature Communications, researchers with the University of Geneva in Switzerland revealed that the crystals allow chameleons to act like selective mirrors, choosing which colors they reflect and which colors they absorb.

"Light will bounce on them only for specific wavelengths" coauthor of the study, Michel Milinkovitch says. "The other wavelengths will not bounce on these cells."

But the amazing ability to change color is not only confined to camouflage. The spectrum-bending species also are able to augment their efficiently organized crystals to produce vibrant coloration that suits their mood. So to test this ability in real time the researchers decided to impose the idea of a threat. By presenting the chameleons with a rival male the researchers were able to film the changes beneath the skin and found the source of the chameleon's nifty trick. And though previous studies believed the chameleons' ability was derived from their pigmentation, this new study reveals these crystals are the true reason why chameleons shine.

"It's a real social display" Milinkovitch says. "It really demonstrates that the color change is happening due to the modification of these crystals."

How could have this trait been evolutionarily derived?

As ectotherms, chameleons rely heavily on the energy that they absorb from the sun to keep their cold-blooded processes working. So while it may seem like a strange ability, this color-changing process may have originally been selected for in nature to better allow chameleon species to absorb light from the sun.